Following his death, the company became state owned, and in 1842, it became known as the Société anonyme pour l'exploitation des établissements de John Cockerill.

In 1807, he moved to Liège and created a factory that constructed machinery for the carding, spinning and weaving of wool,[4] as well as steam engines.

[6] After purchasing the former palace of the Prince-Bishopric of Liège at Seraing in 1817, John and Charles James Cockerill constructed an iron foundry and machine-building factory there.

[10] In 1840, he traveled to Russia in an attempt to raise funds for the company, but he died of typhus on the trip home, leaving no direct heir.

[6] Faced with the prospect of closing an enterprise that employed 30,000 people, the state bought the assets, and on 20 March 1842, the company became known as the Société anonyme pour l'exploitation des établissements de John Cockerill.

In 1865 when the plant at Seraing was visited by a mission from Japan, it was 192 acres (780,000 m2) in size and had two coal mines, as well as facilities for the manipulation of iron and steel, with boiler and locomotive works.

The mechanical engineering part of the Cockerill, which distinguished itself from other Belgian steelmakers, became a separate company in 2002 when it was purchased from Usinor by a private consortium.